Abstract
BackgroundThe 5-year survival rate of cancer patients is the most commonly used statistic to reflect improvements in the war against cancer. This idea, however, was refuted based on an analysis showing that changes in 5-year survival over time bear no relationship with changes in cancer mortality.MethodsHere we show that progress in the fight against cancer can be evaluated by analyzing the association between 5-year survival rates and mortality rates normalized by the incidence (mortality over incidence, MOI). Changes in mortality rates are caused by improved clinical management as well as changing incidence rates, and since the latter can mask the effects of the former, it can also mask the correlation between survival and mortality rates. However, MOI is a more robust quantity and reflects improvements in cancer outcomes by overcoming the masking effect of changing incidence rates. Using population-based statistics for the US and the European Nordic countries, we determined the association of changes in 5-year survival rates and MOI.ResultsWe observed a strong correlation between changes in 5-year survival rates of cancer patients and changes in the MOI for all the countries tested. This finding demonstrates that there is no reason to assume that the improvements in 5-year survival rates are artificial. We obtained consistent results when examining the subset of cancer types whose incidence did not increase, suggesting that over-diagnosis does not obscure the results.ConclusionsWe have demonstrated, via the negative correlation between changes in 5-year survival rates and changes in MOI, that increases in 5-year survival rates reflect real improvements over time made in the clinical management of cancer. Furthermore, we found that increases in 5-year survival rates are not predominantly artificial byproducts of lead-time bias, as implied in the literature. The survival measure alone can therefore be used for a rough approximation of the amount of progress in the clinical management of cancer, but should ideally be used with other measures.
Highlights
Improvements in the 5-year survival rates of cancer patients have long been cited as proof of the increasing effectiveness of anticancer treatment modalities both in scientific articles [1,2,3,4] and in media and policy documents [5]
Data The age-adjusted incidence rates, mortality rates and 5-year survival rates for US patients were obtained from the SEER database using SEERStat
Using the datasets and analytic approaches outlined in Methods, we first investigated the correlation between changes in 5-year survival rates and incidence and mortality rates, as was done by Welch et al [7]
Summary
Improvements in the 5-year survival rates of cancer patients have long been cited as proof of the increasing effectiveness of anticancer treatment modalities both in scientific articles [1,2,3,4] and in media and policy documents [5]. The authors posited that improvements in cancer treatments should simultaneously increase survival rates and reduce mortality rates, leading to a correlation between the two, while improvements in survival rates due to artificial causes (e.g. due to earlier diagnoses) would not be related to decreased mortality. They found no correlation between improving survival rates and decreasing mortality rates, which would seem to suggest that there have been no improvements in cancer management. This idea, was refuted based on an analysis showing that changes in 5-year survival over time bear no relationship with changes in cancer mortality
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